Auto merge of #3254 - rust-lang:rustup-2024-01-06, r=saethlin

Automatic Rustup

2 files changed, 121 insertions, 27 deletions

diff --git a/compiler/rustc_data_structures/src/stable_hasher.rs b/compiler/rustc_data_structures/src/stable_hasher.rs
index 6d75b0fb8a0..afe26f80de8 100644
--- a/compiler/rustc_data_structures/src/stable_hasher.rs
+++ b/compiler/rustc_data_structures/src/stable_hasher.rs
@@ -245,6 +245,32 @@ unsafe impl<T: StableOrd> StableOrd for &T {
     const CAN_USE_UNSTABLE_SORT: bool = T::CAN_USE_UNSTABLE_SORT;
 }
 
+/// This is a companion trait to `StableOrd`. Some types like `Symbol` can be
+/// compared in a cross-session stable way, but their `Ord` implementation is
+/// not stable. In such cases, a `StableOrd` implementation can be provided
+/// to offer a lightweight way for stable sorting. (The more heavyweight option
+/// is to sort via `ToStableHashKey`, but then sorting needs to have access to
+/// a stable hashing context and `ToStableHashKey` can also be expensive as in
+/// the case of `Symbol` where it has to allocate a `String`.)
+///
+/// See the documentation of [StableOrd] for how stable sort order is defined.
+/// The same definition applies here. Be careful when implementing this trait.
+pub trait StableCompare {
+    const CAN_USE_UNSTABLE_SORT: bool;
+
+    fn stable_cmp(&self, other: &Self) -> std::cmp::Ordering;
+}
+
+/// `StableOrd` denotes that the type's `Ord` implementation is stable, so
+/// we can implement `StableCompare` by just delegating to `Ord`.
+impl<T: StableOrd> StableCompare for T {
+    const CAN_USE_UNSTABLE_SORT: bool = T::CAN_USE_UNSTABLE_SORT;
+
+    fn stable_cmp(&self, other: &Self) -> std::cmp::Ordering {
+        self.cmp(other)
+    }
+}
+
 /// Implement HashStable by just calling `Hash::hash()`. Also implement `StableOrd` for the type since
 /// that has the same requirements.
 ///
diff --git a/compiler/rustc_data_structures/src/unord.rs b/compiler/rustc_data_structures/src/unord.rs
index 47c56eba7ad..bd4dff6f62f 100644
--- a/compiler/rustc_data_structures/src/unord.rs
+++ b/compiler/rustc_data_structures/src/unord.rs
@@ -3,9 +3,8 @@
 //! as required by the query system.
 
 use rustc_hash::{FxHashMap, FxHashSet};
-use smallvec::SmallVec;
 use std::{
-    borrow::Borrow,
+    borrow::{Borrow, BorrowMut},
     collections::hash_map::Entry,
     hash::Hash,
     iter::{Product, Sum},
@@ -14,7 +13,7 @@ use std::{
 
 use crate::{
     fingerprint::Fingerprint,
-    stable_hasher::{HashStable, StableHasher, StableOrd, ToStableHashKey},
+    stable_hasher::{HashStable, StableCompare, StableHasher, ToStableHashKey},
 };
 
 /// `UnordItems` is the order-less version of `Iterator`. It only contains methods
@@ -134,36 +133,78 @@ impl<'a, T: Copy + 'a, I: Iterator<Item = &'a T>> UnordItems<&'a T, I> {
     }
 }
 
-impl<T: Ord, I: Iterator<Item = T>> UnordItems<T, I> {
+impl<T, I: Iterator<Item = T>> UnordItems<T, I> {
+    #[inline]
     pub fn into_sorted<HCX>(self, hcx: &HCX) -> Vec<T>
     where
         T: ToStableHashKey<HCX>,
     {
-        let mut items: Vec<T> = self.0.collect();
-        items.sort_by_cached_key(|x| x.to_stable_hash_key(hcx));
-        items
+        self.collect_sorted(hcx, true)
     }
 
     #[inline]
     pub fn into_sorted_stable_ord(self) -> Vec<T>
     where
-        T: Ord + StableOrd,
+        T: StableCompare,
+    {
+        self.collect_stable_ord_by_key(|x| x)
+    }
+
+    #[inline]
+    pub fn into_sorted_stable_ord_by_key<K, C>(self, project_to_key: C) -> Vec<T>
+    where
+        K: StableCompare,
+        C: for<'a> Fn(&'a T) -> &'a K,
     {
-        let mut items: Vec<T> = self.0.collect();
-        if !T::CAN_USE_UNSTABLE_SORT {
-            items.sort();
-        } else {
-            items.sort_unstable()
+        self.collect_stable_ord_by_key(project_to_key)
+    }
+
+    #[inline]
+    pub fn collect_sorted<HCX, C>(self, hcx: &HCX, cache_sort_key: bool) -> C
+    where
+        T: ToStableHashKey<HCX>,
+        C: FromIterator<T> + BorrowMut<[T]>,
+    {
+        let mut items: C = self.0.collect();
+
+        let slice = items.borrow_mut();
+        if slice.len() > 1 {
+            if cache_sort_key {
+                slice.sort_by_cached_key(|x| x.to_stable_hash_key(hcx));
+            } else {
+                slice.sort_by_key(|x| x.to_stable_hash_key(hcx));
+            }
         }
+
         items
     }
 
-    pub fn into_sorted_small_vec<HCX, const LEN: usize>(self, hcx: &HCX) -> SmallVec<[T; LEN]>
+    #[inline]
+    pub fn collect_stable_ord_by_key<K, C, P>(self, project_to_key: P) -> C
     where
-        T: ToStableHashKey<HCX>,
+        K: StableCompare,
+        P: for<'a> Fn(&'a T) -> &'a K,
+        C: FromIterator<T> + BorrowMut<[T]>,
     {
-        let mut items: SmallVec<[T; LEN]> = self.0.collect();
-        items.sort_by_cached_key(|x| x.to_stable_hash_key(hcx));
+        let mut items: C = self.0.collect();
+
+        let slice = items.borrow_mut();
+        if slice.len() > 1 {
+            if !K::CAN_USE_UNSTABLE_SORT {
+                slice.sort_by(|a, b| {
+                    let a_key = project_to_key(a);
+                    let b_key = project_to_key(b);
+                    a_key.stable_cmp(b_key)
+                });
+            } else {
+                slice.sort_unstable_by(|a, b| {
+                    let a_key = project_to_key(a);
+                    let b_key = project_to_key(b);
+                    a_key.stable_cmp(b_key)
+                });
+            }
+        }
+
         items
     }
 }
@@ -268,16 +309,30 @@ impl<V: Eq + Hash> UnordSet<V> {
     }
 
     /// Returns the items of this set in stable sort order (as defined by
-    /// `StableOrd`). This method is much more efficient than
+    /// `StableCompare`). This method is much more efficient than
     /// `into_sorted` because it does not need to transform keys to their
     /// `ToStableHashKey` equivalent.
     #[inline]
-    pub fn to_sorted_stable_ord(&self) -> Vec<V>
+    pub fn to_sorted_stable_ord(&self) -> Vec<&V>
     where
-        V: Ord + StableOrd + Clone,
+        V: StableCompare,
     {
-        let mut items: Vec<V> = self.inner.iter().cloned().collect();
-        items.sort_unstable();
+        let mut items: Vec<&V> = self.inner.iter().collect();
+        items.sort_unstable_by(|a, b| a.stable_cmp(*b));
+        items
+    }
+
+    /// Returns the items of this set in stable sort order (as defined by
+    /// `StableCompare`). This method is much more efficient than
+    /// `into_sorted` because it does not need to transform keys to their
+    /// `ToStableHashKey` equivalent.
+    #[inline]
+    pub fn into_sorted_stable_ord(self) -> Vec<V>
+    where
+        V: StableCompare,
+    {
+        let mut items: Vec<V> = self.inner.into_iter().collect();
+        items.sort_unstable_by(V::stable_cmp);
         items
     }
 
@@ -483,16 +538,16 @@ impl<K: Eq + Hash, V> UnordMap<K, V> {
         to_sorted_vec(hcx, self.inner.iter(), cache_sort_key, |&(k, _)| k)
     }
 
-    /// Returns the entries of this map in stable sort order (as defined by `StableOrd`).
+    /// Returns the entries of this map in stable sort order (as defined by `StableCompare`).
     /// This method can be much more efficient than `into_sorted` because it does not need
     /// to transform keys to their `ToStableHashKey` equivalent.
     #[inline]
-    pub fn to_sorted_stable_ord(&self) -> Vec<(K, &V)>
+    pub fn to_sorted_stable_ord(&self) -> Vec<(&K, &V)>
     where
-        K: Ord + StableOrd + Copy,
+        K: StableCompare,
     {
-        let mut items: Vec<(K, &V)> = self.inner.iter().map(|(&k, v)| (k, v)).collect();
-        items.sort_unstable_by_key(|&(k, _)| k);
+        let mut items: Vec<_> = self.inner.iter().collect();
+        items.sort_unstable_by(|(a, _), (b, _)| a.stable_cmp(*b));
         items
     }
 
@@ -510,6 +565,19 @@ impl<K: Eq + Hash, V> UnordMap<K, V> {
         to_sorted_vec(hcx, self.inner.into_iter(), cache_sort_key, |(k, _)| k)
     }
 
+    /// Returns the entries of this map in stable sort order (as defined by `StableCompare`).
+    /// This method can be much more efficient than `into_sorted` because it does not need
+    /// to transform keys to their `ToStableHashKey` equivalent.
+    #[inline]
+    pub fn into_sorted_stable_ord(self) -> Vec<(K, V)>
+    where
+        K: StableCompare,
+    {
+        let mut items: Vec<(K, V)> = self.inner.into_iter().collect();
+        items.sort_unstable_by(|a, b| a.0.stable_cmp(&b.0));
+        items
+    }
+
     /// Returns the values of this map in stable sort order (as defined by K's
     /// `ToStableHashKey` implementation).
     ///